content: /*
   * Copyright 2017 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package hu.akarnokd.reactive4javaflow.impl.operators;
  
  import hu.akarnokd.reactive4javaflow.*;
  import hu.akarnokd.reactive4javaflow.impl.DeferredScalarSubscription;
  
  import java.util.concurrent.Flow;
  
  public final class FolyamElementAt<T> extends Esetleg<T> {
  
      final Folyam<T> source;
  
      final long index;
  
      public FolyamElementAt(Folyam<T> source, long index) {
          this.source = source;
          this.index = index;
      }
  
      @Override
      protected void subscribeActual(FolyamSubscriber<? super T> s) {
          source.subscribe(new ElementAtSubscriber<>(s, index));
      }
  
      static final class ElementAtSubscriber<T> extends DeferredScalarSubscription<T> implements FolyamSubscriber<T> {
  
          Flow.Subscription upstream;
  
          long index;
  
          public ElementAtSubscriber(FolyamSubscriber<? super T> actual, long index) {
              super(actual);
              this.index = index;
          }
  
          @Override
          public void onSubscribe(Flow.Subscription subscription) {
              upstream = subscription;
              actual.onSubscribe(this);
              subscription.request(Long.MAX_VALUE);
          }
  
          @Override
          public void onNext(T item) {
              long idx = index;
              if (idx == 0L) {
                  upstream.cancel();
                  complete(item);
              }
              index = idx - 1;
          }
  
          @Override
          public void onError(Throwable throwable) {
              error(throwable);
          }
  
          @Override
          public void onComplete() {
              if (index >= 0L) {
                  complete();
              }
          }
  
          @Override
          public void cancel() {
              super.cancel();
              upstream.cancel();
          }
      }
  }
  